This invention relates to a technique for locating each of a plurality of buried utility conveyances belonging to the same service provider.
Many utilities and telecommunication service providers such as ATandT, bury their pipes and cables hereinafter, xe2x80x9cutility conveyancesxe2x80x9d) underground, especially in urban environments, both for reasons for safety and esthetics. The service provider undertaking burial of a conveyance (or the contractor working on behalf of the provider) will typically map the location of the conveyance to facilitate subsequent repair. While such mapping provides a general indication of the location of the buried conveyance, greater precision often becomes necessary, especially when an excavating contractor seeks to excavate in an area in close proximity to the conveyance. For this reason, many service providers that maintain underground utility conveyances such as ATandT employ electromagnetic signaling to precisely locate a buried conveyance in advance of any nearby excavation.
To precisely locate a buried conveyance via electromagnetic signaling, the service provider will impress on the conveyance a locating signal whose frequency is unique to that service provider. To locate a conveyance, a technician employs a receiver, such as an LMS 4 receiver manufactured by Radiodetection, Inc of Mahwah, N.J., to detect the particular locating signal radiated by the conveyance of interest.
In many instances, several buried utility conveyances will run along the same right-of-way. Attempting to locate a specific one of such buried conveyances can prove problematic because the locating signals of adjacent conveyances often interfere, thereby producing xe2x80x9cfalsexe2x80x9d locates. As disclosed in our U.S. Pat. No. 5,644,237, issued Jul. 1, 1997, and assigned in the name of ATandT, we have greatly reduced the incidence of false locates by impressing a pulsed confirmation signal on the conveyance in addition to the conventional locate signal. The confirmation signal is unique to the conveyance so that by monitoring for both the locate and confirmation signals, a technician can precisely locate a particular conveyance of interest.
Often, a single service provider will bury several conveyances along the same right-of-way. While the locating technique claimed in our ""237 patent allows a technician to locate an individual conveyance running along such a right-of-way, the technique provides no mechanism for alerting the technician of the total number of conveyances on the same right-of-way belonging to the same service provider. Thus, a technician may locate one or even two conveyances belonging to a service provider, but not know additional that conveyances exist which the technician must locate as well.
Thus, there is need for a technique that provides additional information to a technician regarding the number of buried conveyances of a single service provider running along a common right-of-way.
Briefly, in accordance with a preferred embodiment, the present invention provides a method for identifying multiple buried conveyances of a single service provider running along a common right-of-way. The method of the invention is practiced by impressing a locate signal of a particular frequency on each buried conveyance of the same service provider on common right-of-way. In addition, each buried conveyance of the same service provider also carries a unique pulsed confirmation signal specific to that conveyance. In accordance with the present invention, the pulsed confirmation signal on each conveyance not only identifies the conveyance itself but also provides an indication of the number of other conveyances belonging to the same provider on the right-of-way. The pulsed confirmation signal on each buried conveyance will indicate its particular relationship (e.g., the first, second, third, etc.) to the total number of such conveyances. Thus, when a technician receives both the locate and confirmation signals via a receiver designed for this purpose to locate one of the buried conveyances of the same service provider, the technician will immediately know how many other conveyances belong to the same provider and also require location.